Discrete time loop based thermal control

Abstract

In an embodiment, a circuit includes: an error amplifier; a temperature sensor, wherein the temperature sensor is coupled to the error amplifier; a discrete time controller coupled to the error amplifier, wherein the discrete time controller comprises digital circuitry; a multiple bits quantizer coupled to the discrete time controller, wherein the multiple bits quantizer produces a digital code output; and a heating array coupled to the multiple bits quantizer, wherein the heating array is configured to generate heat based on the digital code output.

What is claimed is: 
     
       1. A discrete time loop based control system, comprising:
 an error amplifier having a first input configured to receive a reference signal; 
 a temperature sensor coupled to a second input of the error amplifier; 
 a discrete time controller coupled to an output of the error amplifier, wherein the discrete time controller comprises digital circuitry; and 
 a quantized plant comprising a quantizer that produces a digital code for control of a heater, wherein the temperature sensor produces a value that characterizes the digital code output by the quantizer, wherein the heater comprises a heating array, wherein the heating array comprises a plurality of heating elements arranged in parallel, wherein each of the plurality of heating elements comprises a respective resistor coupled to a respective switch, wherein the respective switch is controlled by a respective bit of the digital code output, wherein the temperature sensor is surrounded by the plurality of heating elements, and wherein the discrete time controller is configured to produce a control signal for controlling the quantized plant. 
 
     
     
       2. The system of  claim 1 , wherein the discrete time controller is an integrator controller. 
     
     
       3. The system of  claim 2 , wherein the integrator controller comprises an operational amplifier with a first capacitor between an inverting input and an output. 
     
     
       4. The system of  claim 3 , wherein, at the operational amplifier, the inverting input is connected with a second switch and a non-inverting input is coupled to the ground. 
     
     
       5. The system of  claim 4 , wherein, the second switch is coupled to a third switch and a second capacitor. 
     
     
       6. The system of  claim 5 , wherein the second switch is driven by a first clock signal and the third switch is driven by a second clock signal, wherein the first clock signal and the second clock signal are non-overlapping clock signals with a same period. 
     
     
       7. The system of  claim 1 , wherein the digital code output comprises multiple bits that are each configured to control the plurality of heating elements. 
     
     
       8. The system of  claim 7 , wherein the discrete time controller is a proportional and integrator controller. 
     
     
       9. The system of  claim 7 , wherein the discrete time controller is a proportional integral derivative controller. 
     
     
       10. The system of  claim 7 , wherein each of the plurality of heating elements comprises a resistor with one end coupled to a voltage source and another end coupled to a switch to the ground. 
     
     
       11. A circuit, comprising:
 an error amplifier; 
 a sensor, wherein the sensor is coupled to the error amplifier; 
 a discrete time controller coupled to an output of the error amplifier; and 
 a quantized plant comprising a quantizer that produces a digital code for control of a heater, wherein the sensor produces a value that characterizes the digital code output by the quantizer, wherein the heater comprises a heating array, wherein the heating array comprises a plurality of heating elements arranged in parallel, wherein the sensor is surrounded by the plurality of heating elements, wherein each of the plurality of heating elements comprises a respective resistor coupled to a respective switch, wherein the respective switch is controlled by a respective bit of the digital code output, and wherein the discrete time controller is configured to produce a control signal for controlling the quantized plant. 
 
     
     
       12. The circuit of  claim 11 , wherein the heating array is coupled to the quantizer, wherein the digital code is utilized by the heating array to control different switches within the array. 
     
     
       13. The circuit of  claim 12 , wherein the plurality of heating elements are monotonic. 
     
     
       14. The circuit of  claim 11 , wherein the sensor is a temperature sensor. 
     
     
       15. The circuit of  claim 11 , wherein the quantizer is a multiple bit quantizer. 
     
     
       16. A method, comprising:
 producing an output of a process based on a reference value input, wherein the output is a temperature; 
 determining an output measurement value based on the output using a temperature sensor; 
 determining an error between the output measurement value and the reference value input; 
 generating a control signal based on the error; and 
 using the control signal to control the process with a quantizer, wherein the quantizer utilizes the control signal to generate a digital code, and wherein the digital code individually controls different coils of a heating array, wherein the heating array comprises a plurality of heating elements arranged in parallel, wherein each of the plurality of heating elements comprises a respective resistor coupled to a respective switch, wherein the respective switch is controlled by a respective bit of the digital code output, wherein the temperature sensor is surrounded by the plurality of heating elements. 
 
     
     
       17. The method of  claim 16 , wherein the quantizer comprises a multiple bit quantizer, and the process is performed by the multiple bit quantizer. 
     
     
       18. The method of  claim 17 , further comprising turning the heating array on or off based on the process. 
     
     
       19. The method of  claim 17 , further comprising turning different coils of the heating array on or off based on the digital code produced by the multiple bit quantizer. 
     
     
       20. The method of  claim 16 , wherein the discrete time controller is implemented in digital circuitry.